Radioactive materials such as vitrified radioactive fission products or irradiated nuclear fuel elements have to be placed in special containers for the purpose of transport and storage. The containers have a high shielding to radiation and a sufficient cooling surface as well as a high stability. Metal containers guarantee a safe enclosure for radioactive waste products. The metal containers are open only at one end and it is this opening through which the materials to be stored are passed.
After filling a container destined for terminal storage with glass from highly radioactive fission products, it has been conventional practice to place a cylindrical cover in the open end of the vessel and to weld the cover to the abutting container rim. By means of the tight seal of the vessel with the sealing cover, it was believed that the radioactive materials or materials damaging to living organisms could be safely separated from the ambient.
The results obtained up until now with this procedure have been unsatisfactory. The welding activity has to be carried out in a so-called "hot cell." Accordingly, it was necessary to conduct the welding operation from a remote location with the aid of remotely-controlled apparatus. Up to now, the desired impermeability of the seal to gas of 10.sup.-3 Torr Liter/Second could not be obtained with certainty and reproducibility. The operating person carrying out the welding operation must necessarily perform each welding operation individually and always with a different quality.